Iron type golf club head

ABSTRACT

An iron type golf club head including a face portion having a planar face surface, and a hosel portion connected to the heel side of the face portion. A shaft insertion hole is provided in the hosel portion so as to penetrate the hosel portion. The distance from the center of gravity is 28-33 mm, the height of the center of gravity is 12-21 mm, the depth of the center of gravity is 5-15 mm, and the goose distance is 4-15 mm.

[0001] The present disclosure relates to the subject matter contained in Japanese Patent Application No. 2002-1540 filed on Jan. 8, 2002, which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an iron type golf club head, and particularly relates to an iron type golf club head applicable to a long iron having a small loft angle.

[0004] 2. Description of the Related Art

[0005] As known well, an iron type golf club head has a face portion having a planar face surface, and a hosel portion connected to the heel side of the face portion and provided with a shaft insertion hole. A shaft is inserted into the shaft insertion hole and fixedly attached thereto by a bonding agent. A distance (distance in front view) between the center of gravity of the golf club head and the extension of the shaft axis is called a distance from the center of gravity.

[0006] A long iron is a club difficult for beginners to make a good shot because it has a smaller loft angle and a longer shaft than that of a short iron. Thus, the long iron is apt to be kept away from the beginners. In order to make the long iron easy to hit a shot, there has been an attempt that the golf club head of the long iron is enlarged to increase its sweet area. However, when the golf club head is enlarged, the distance from the center of gravity is increased and the height of the center of gravity is also increased. As a result, it is difficult for beginners or powerless golfers to hit a ball high or the hit ball is apt to travel to the right (in the case of right-handed golfers, the same thing will be applied hereinafter) or slice heavily.

SUMMARY OF THE INVENTION

[0007] It is an object of the invention to provide a golf club having an iron type golf club head small in loft angle, with which club it is easy even for beginners or powerless golfers to hit a ball high.

[0008] The iron type golf club head according to the invention has a loft angle of 15-25°, and has a feature in that the distance from the center of gravity is 28-33 mm, and the height of the center of gravity is 12-21 mm.

[0009] In such an iron type golf club head, each of the distance from the center of gravity and the height of the center of gravity is smaller than that in a long iron head in the related art. Thus, it becomes easy to hit a ball high even if a beginner uses a long iron having the golf club head.

[0010] According to the invention, it is preferable that the depth of the center of gravity from the face surface is 5-15 mm, and the goose distance is 4-15 mm. In addition, it is desirable that the circumferential edge portion of the face surface is made of a material different in specific gravity from the material of the area inside the circumferential edge portion, and the specific gravity of the material of the inside area is smaller than that of the material of the circumferential edge portion.

[0011] The definitions of the loft angle, the distance from the center of gravity, the height of the center of gravity, the goose distance and so on in the invention will be described with reference to FIGS. 6 and 7.

[0012] First, a shaft is attached to a golf club head, and the shaft is attached to a lie angle measuring instrument. The lie angle measuring instrument chucks the shaft so that the shaft axis always stays in a vertical plane. Then, the face surface is adjusted to be square to a target. In addition, the sole surface of the golf club head is adjusted so that toe-side and heel-side gaps α₁ and α₂ are equal to each other with respect to a reference plane (the level of a horizontal surface plate). Incidentally, it is assumed that the sole surface between the left end and the right end of corrugations (grooves long from side to side in the face surface) is tangent to the reference plane. The length of the corrugations is typically about 54-58 mm. After that, the crossing angle of the reference plane and the shaft axis (according with the axis of the hosel portion) is measured, and this is regarded as the lie angle.

[0013] The distance between the center of gravity G and the shaft axis in the front view of FIG. 6 (in which the face surface is viewed from the square direction and projected on a plane perpendicular to the reference plane) is the distance from the center of gravity. In addition, the distance between the reference plane and the center of gravity G is the height of the center of gravity. The distance between a plane F₁ closest to the toe side and a plane F₂ closest to the heel side of planes perpendicular to the reference plane and tangent to a plane parallel with the face square direction is the face portion length.

[0014] As shown in FIG. 7, the distance between the face surface and the center of gravity G is the depth of the center of gravity. The crossing angle of the face surface and the shaft axis in the side view of FIG. 7 is the loft angle. The distance between the foremost end of the face surface and a plane F₃ including the foremost edge of the hosel portion (this plane F₃ is perpendicular to the face square direction) is the goose distance. The distance between the face surface and a plane F₄ including the rearmost end (rearmost end in a direction perpendicular to the face surface) of the golf club head is the maximum thickness of the golf club head.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a front view of an iron type golf club head according to an embodiment;

[0016]FIG. 2 is a side view of the iron type golf club head according to the embodiment;

[0017]FIG. 3 is a sectional view taken on line III-III in FIG. 1;

[0018]FIG. 4 is a perspective view of the golf club head according to the embodiment, viewed from its front;

[0019]FIG. 5 is a perspective view of the golf club head according to the embodiment, viewed from its rear;

[0020]FIG. 6 is a view for explaining a method of measuring characteristic values of a golf club head; and

[0021]FIG. 7 is a view for explaining the method of measuring characteristic values of a golf club head.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Description will be made below on an embodiment with reference to the drawings. FIG. 1 is a front view of an iron type golf club head according to an embodiment. FIG. 2 is a side view of the iron type golf club head according to the embodiment. FIG. 3 is a sectional view taken on line III-III in FIG. 1. FIG. 4 is a perspective view of the golf club head according to the embodiment, viewed from its front. FIG. 5 is a perspective view of the golf club head according to the embodiment, viewed from its rear.

[0023] This iron type golf club head 1 has a face portion 2 and a hosel portion 3. The face portion 2 has a planar face surface 2f, and the hosel portion 3 is connected to the heel side of the face portion 2. A shaft insertion hole 4 is provided in the hosel portion 3 so as to penetrate the hosel portion 3. The shaft insertion hole 4 as a whole is disposed in front of a plane including the face surface 2f so as to form a so-called goose neck, as shown in FIG. 2.

[0024] Since the invention is suitably applied to a long iron, the loft angle is set to be 15-25°. Incidentally, it is preferable that the club length of the long iron is 38-42 inches (965-1,067 mm), particularly 38.5-41 inches (975-1,042 mm).

[0025] The distance from the center of gravity is set to be 28-33 mm, preferably 29-32 mm. When the distance from the center of gravity is larger than this range, it becomes difficult particularly for beginners to turn the head so that a hit ball is apt to travel to the right or slice. On the contrary, when the distance from the center of gravity is smaller than this range, it becomes easy to turn the head excessively so that a missed shot called a smothered ball or an excessive hook ball is apt to appear.

[0026] The height of the center of gravity is set to be 12-21 mm. The lower limit is preferably not smaller than 13 mm. It is preferable that the upper limit is not larger than 21 mm, especially not larger than 19mm, more especially not larger than 18 mm. When the height of the center of gravity of the golf club head is made lower than that in the related art, it becomes easy to hit a ball high. Incidentally, since the diameter of a golf ball is about 43 mm, it is desirable that the height of the center of gravity is lower than half the diameter (21.5 mm). Thus, the upper limit is set at 21 mm. Technically, it is possible to make the height of the center of gravity lower than 12 mm when the height of the face portion 2 is reduced. In this case, however, the vertical width of the sweet area is reduced, or there arises the feeling of insecurity to the eyes of beginners (the feeling of insecurity that it may be difficult to hit a ball on the face), or a missed shot caused by the golf club head sneaking through the lower side of the ball is produced in the rough easily. Accordingly, the lower limit of the height of the center of gravity is set at 12 mm.

[0027] Incidentally, in order to reduce the height of the center of gravity, a high specific gravity material 6 may be embedded in the sole portion. The high specific gravity material preferably has a specific gravity of 8 or higher. Specifically, tungsten, a tungsten alloy, a copper alloy or the like is preferable. When the high specific gravity material is disposed close to the rear (back surface side) of the sole portion, the center of gravity is close to the heel, and the depth of the center of gravity can be increased, as will be described later.

[0028] The depth of the center of gravity is preferably 5-15 mm, more preferably 6-12 mm. When the depth of the center of gravity is made larger than that in the related art, it becomes easy to hit a ball high. However, when the depth of the center of gravity is made larger than 15 mm, the sole thickness increases correspondingly so that it becomes difficult to hit a ball sinking in the rough or a ball in a divot correctly. Thus, the upper limit of the depth of the center of gravity is set at 15 mm.

[0029] Incidentally, in order to increase the depth of the center of gravity, the high specific gravity material may be provided on the back surface side of the sole bottom surface, or in the lower portion of the back surface of the face portion.

[0030] It is preferable that the sole maximum thickness is 15-35 mm, especially 18-30 mm. When the sole maximum thickness is smaller than 15 mm, the golf club head becomes easy to eat the ground at the time of a fat shot (meaning a shot in which the golf club head hits the ground short of a ball). On the contrary, when the sole thickness is larger than 35 mm, it becomes difficult to hit a ball sinking in the rough or a ball in a divot correctly.

[0031] It is preferable that the goose distance is 4-15 mm. Particularly, it is preferable that the lower limit value of the goose distance is not smaller than 6 mm, especially not smaller than 8 mm, and the upper limit value thereof is not larger than 12 mm.

[0032] When the goose distance is made large to be not smaller than 4 mm, it becomes easy to turn the golf club head so that the probability of a missed shot traveling to the right is reduced. However, when the goose distance is larger than 15 mm, the difference from the goose distance of the golf club head in the related art is so significant that a missed shot is apt to be hit or it takes much time unnecessarily for a user to adapt himself or herself to the golf club head.

[0033] According to the invention, in order to increase the moment of inertia around the axis of the center of gravity to thereby expand the sweet area or in order to increase the depth of the center of gravity, the circumferential edge portion of the face portion may be made of a steel material such as stainless steel or marageing steel while disposing a lower specific gravity material in the area inside the circumferential edge portion. Incidentally, the specific gravity of stainless steel or marageing steel is about 7-8. Examples of such lower specific gravity materials include titanium, titanium alloys, aluminum alloys, magnesium alloys, and fiber reinforced resin (for example, carbon fiber reinforced resin), which are materials having a specific gravity of about 1.3-5.

[0034] Incidentally, in this embodiment, a crossing point P of the axis of the shaft insertion hole 4 and the lower end surface of the hosel portion 3 is located under an upper edge 2t of the face portion 2 and above a lower edge 2b of the face portion, as illustrated in FIG. 1.

[0035] In addition, in this embodiment, the axial length of the shaft insertion hole 4 is preferably 25-35 mm, more preferably 27-32 mm. Further, in this embodiment, the lower end surface of the hosel portion 3 is formed into a slope which is oblique with respect to the axis of the shaft insertion hole 4 so that a part closer to the lower end in the axial direction of the shaft insertion hole 4 is closer to the face surface 2f.

[0036] More accurately, the point P is defined as a crossing point of the axis of the shaft insertion hole 4 and a plane including the lower end surface of the hosel portion 3. The plane including the lower end surface of the hosel portion 3 (hereinafter referred to as “hosel portion lower end surface” occasionally) is formed into a slope in which a part closer to the lower end in the axial direction of the shaft insertion hole 4 is closer to the face surface 2f as described above. The hosel portion lower end surface looks to the front lower portion of the face portion 2. In this embodiment, the hosel portion lower end surface is bent to be slightly concave in its section taken on a plane perpendicular to the hosel portion lower end surface and including the axis of the shaft insertion hole.

[0037] It is preferable that the angle with which a plane tangent to the hosel portion end surface crosses the face surface 2f at the point P where the plane including the lower end surface of the hosel portion 3 crosses the axis of the shaft insertion hole 4 is 120-155°, especially 125-150°.

[0038] The tip of the shaft is inserted into the shaft insertion hole 4 of the golf club head 1 and fixedly attached thereto by a bonding agent. The tip of the shaft is ground to be flush with the lower end surface of the hosel portion 3. When the shaft is hollow, the shaft tip is sealed off with a filler. This filler is also ground to be flush with the lower end surface of the hosel portion 3.

[0039] Since the shaft insertion hole 4 penetrates the hosel portion 3 in such a manner, the axial length of the shaft insertion hole 4 (the distance between the point P and the upper end surface of the hosel portion 3) can be secured to be not smaller than 25 mm even if the length of the hosel portion 3 as a whole is reduced. Thus, the hosel portion 3 and the shaft can be fixedly attached to each other sufficiently firmly. Then, by reducing the length of the hosel portion 3 in such a manner, the upward protrusion length of the hosel portion 3 is reduced so that the center of gravity of the golf club head 1 is lowered. Thus, with the golf club provided with the golf club head 1 whose center of gravity is low, it is easy even for high handicapped golfers or low head speed golfers to hit a ball high.

[0040] Incidentally, it is preferable that the hosel height is 40-57 mm, especially 40-53 mm. Since the hosel portion is substantially cylindrical, the hosel height is defined as the distance between the center point of the upper end surface of the hosel portion and the reference plane.

[0041] In addition, when the shaft insertion hole 4 penetrates the hosel portion 3, there is no metal material provided for closing the lower portion of the shaft insertion hole, unlike the related art. The golf club head is lightened by the weight of the metal material. For example, when the weight by which the golf club head is lightened is added to the sole of the golf club head, the golf club head can be made lower in the position of the center of gravity than that in the related art though the total weight of the golf club head is equal to that in the related art.

[0042] The golf club head 1 has a shape in which the face surface side of the lower end portion of the hosel portion 3 is cut obliquely. Thus, it is difficult to hit a shank (hit a ball with a socket).

[0043] Incidentally, according to the invention, it is preferable to adopt a cavity back structure in which a concave portion 5 is provided in the central portion of the back surface as shown in FIG. 5. In addition, it is preferable to adopt a structure in which the thickness is increased both on the heel side and on the toe side. Such a shape is formed for expanding the sweet area of the golf club head.

[0044] The golf club head 1 having a shape shown in FIGS. 1 to 5 was manufactured out of a titanium alloy having a specific gravity of about 5 as its metal material, while a tungsten alloy having a specific gravity of about 12 was embedded in the sole portion. Table 1 shows the characteristic of this golf club head. Incidentally, Table 1 also shows the measurement result of the characteristic of a commercially available product having the same loft angle.

[0045] Incidentally, the outer diameter of the hosel portion 3 was made 13 mm, the inner diameter of the shaft insertion hole 4 was made 9.4 mm, the axial length of the shaft insertion hole 4 was made 30 mm, and the lie angle was made 60°. TABLE 1 loft angle distance from center height of center depth of center sole maximum goose No. (degree) of gravity (mm) of gravity (mm) of gravity (mm) thickness (mm) distance (mm) Example 23° 31.8 17.5 6.8 28.4 10.2 Comp. 23° 35.7 21.5 2.2 18.9 3.6 Example

[0046] A carbon shaft was attached to each of the golf club heads so as to manufacture a golf club (long iron) having a club length of 38.5 inches (978 mm). Thus, evaluation was made by trial shots. As a result, a high handicapped golfer could not hit any shot but a ground ball to the right using the golf club with the iron type golf club head in Comparative Example. On the other hand, the high handicapped golfer could hit a ball substantially straightly about 170 yards repeatedly using the golf club with the iron type golf club head according to the invention.

[0047] As described above, according to the invention, a golf club head is provided in which the center of gravity is low, and with which it is easy even for beginners to hit a ball high, while there is a little fear that a hit ball travels to the right or slices. 

What is claimed is:
 1. An iron type golf club head comprising: a face portion having a face surface; a hosel portion connected to a heel side of the face portion; and a sole portion; wherein a loft angle is 15-25°; wherein a distance from a center of gravity is 28-33 mm; and height of the center of gravity is 12-21 mm.
 2. The golf club head according to claim 1, wherein depth of the center of gravity from the face surface is 5-15 mm.
 3. The golf club head according to claim 1, wherein a goose distance is 4-15 mm.
 4. The golf club head according to claim 1, wherein the face portion has a circumferential edge portion and an inside portion; wherein the circumferential edge portion and the inside portion are made of different materials; and wherein specific gravity of the material of the inside portion is smaller than specific gravity of the material of the circumferential edge portion.
 5. The golf club head according to claim 1, wherein a high specific gravity member is provided in the sole portion; and wherein the high specific gravity member is disposed near or behind a longitudinal midpoint of the sole portion.
 6. The golf club head according to claim 1, wherein, the distance from the center of gravity is 29-32 mm.
 7. The golf club head according to claim 1, wherein the height of the center of gravity is 13-19 mm.
 8. The golf club head according to claim 1, wherein the depth of the center of gravity is 6-12 mm.
 9. The golf club head according to claim 1, wherein the goose distance is 6-12 mm.
 10. The golf club head according to claim 4, wherein the specific gravity of the circumferential edge portion is 7-8; and the specific gravity of the inside portion is 1.3-5.
 11. An iron type golf club comprising: a head; and a shaft; wherein the head includes: a face portion having a face surface; a hosel portion connected to a heel side of the face portion and defining a through-hole; and a sole portion; wherein the shaft is inserted into the through-hole; wherein a loft angle of the head is 15-25°; wherein a distance from a center of gravity of the head is 28-33 mm; and wherein height of the center of gravity is 12-21 mm.
 12. The golf club according to claim 11, wherein depth of the center of gravity from the face surface is 5-15 mm.
 13. The golf club according to claim 11, wherein a goose distance of the head is 4-15 mm.
 14. The golf club according to claim 11, wherein the face portion has a circumferential edge portion and an inside portion; wherein the circumferential edge portion and the inside portion are made of different materials; and wherein specific gravity of the material of the inside portion is smaller than specific gravity of the material of the circumferential edge portion.
 15. The golf club according to claim 11, wherein a high specific gravity member is provided in the sole portion; and wherein the high specific gravity member is disposed near or behind a longitudinal midpoint of the sole portion.
 16. The golf club according to claim 11, wherein the distance from the center of gravity of the head is 29-32 mm.
 17. The golf club according to claim 11, wherein the height of the center of gravity of the head is 13-19 mm.
 18. The golf club according to claim 11, wherein the depth of the center of gravity of the head is 6-12 mm.
 19. The golf club according to claim 11, wherein the goose distance of the head is 6-12 mm.
 20. The golf club according to claim 14, wherein the specific gravity of the circumferential edge portion is 7-8; and wherein the specific gravity of the inside portion is 1.3-5. 